


The Ocean's Darkness

by Life_sans_Sin



Series: Reader Sins [8]
Category: Undertale (Video Game)
Genre: Dubious Consent, F/M, Gift Fic, May be continued sometime later I don't know yet, Merman W.D. Gaster, Multiple Orgasms, Octopus Mermaid, Plot What Plot/Porn Without Plot, Reader has female parts, Tagged as Non-con for safety, Tentacles, They start off not wanting it then decides they're into it, birthday gift
Language: English
Status: In-Progress
Published: 2018-08-19
Updated: 2018-08-19
Packaged: 2019-06-29 20:45:52
Rating: Explicit
Warnings: Rape/Non-Con
Chapters: 1
Words: 1,456
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15737028
Author URL: https://archiveofourown.org/users/Life_sans_Sin/pseuds/Life_sans_Sin
Summary: You had been warned about rip tides. You'd been warned that they pull you someplace dark, darker, yet darker...But the little spots of violet light guide you. He decided to save you, and He seems to have something he wants from you in return.Will you be able to escape the Beast of the Deep, or will he consume you..?(Notes: Happy Birthday Sweets!!)





	The Ocean's Darkness

**Author's Note:**

  * For [NihilismPastry](https://archiveofourown.org/users/NihilismPastry/gifts).



You didn’t know his name, just that he went by Gaster… at least, that’s what the locals called him.

 

He came across you when you were pulled out by the rip tide, legs kicking frantically to swim sideways, out of the rip, but to no avail. You were pulled right down the center of it, further and further out to sea.

 

Night fell, and you floated the best you could, your arms and legs burning from extended exertion. The water around you was dark, darker, yet darker still, somehow. It looked black as pitch, like a pane of black glass surrounding you, pulling you downward, downward, downward…

 

Your lips brushed the surface of the inky darkness and you gasped, kicking your lethargic legs to try and kick yourself higher. You were able to draw one last breath before you finally sunk.

 

The salt water stung your eyes, but you refused to close them. Sharks were known to swim in this area, especially at nighttime, after the tourists had all gone home, and you wanted to know what was coming for you… if anything.

 

Then, suddenly, a bright series of purple lights cut through the darkness, dim at first, then slowly growing closer. Bio-luminescence wasn’t uncommon among seafaring creatures, that much you knew, but you had never seen anything so… unusual.

 

The water was dark, darker, darker still, but even as your lungs burned, and your mind grew dizzy, you felt yourself reaching out toward those lights.

 

Your vision grew dark around the edges, dark, darker, darker still… and then, suddenly, something hard and cold grasped around your waist, and you were thrusted upwards, out from beneath the ocean waves. You pulled in deep, shuddering breaths, wheezing and coughing violently, clinging onto the cold  solidness that had saved you.

 

You had heard of him from the locals, but seeing him was… an experience all its own.

 

Deep, black sockets stared back at you and, instead of eyes, there were small pinpricks of light, soft in their appearance. Yet they cast no light on you.

 

Your eyes flickered downward, and you saw a spine connected to the skull looking at you, and ribs that expanded with breath, however odd a concept that was. Yet despite all the hard bone, you felt something slick against your legs, like tendrils. A glance further down revealed tentacles, like those of an octopus, but along the tops of each one were dotted with purple lights, bio-luminescence, you figured.

 

You clung to him.. or what you assumed was a him. If the thick cock pressing against your stomach had anything to say about it, it was definitely a him.

 

… Wait, what?

 

Suddenly your swimsuit is ripped from your body, and you let out a yelp of indignation and shock. His smooth mouth curved downward into a frown when you began to struggle, trying to pull away from him, and a tentacle wrapped around each of your legs, holding you still. You couldn’t swim. You couldn’t swim away from him. Hell, all he’d have to do was let you go and you’d probably just go back to drowning.

 

A low hum rose from his throat(?) and you stiffened when his tentacles spread your legs, another rising up to brush against the inside of your thigh. You closed your eyes tightly and prayed that he would just let you go, that he’d help you get back to shore and just… not do what was apparently going to be happening.

 

The smooth, slimy texture of a tentacle brushed against your outer lips, and you shivered, trying desperately to close your legs, but to no avail. It wriggled against you for a moment before pressing in between your labia to brush against your clit. It drew slow, lazy circles around it, and you shook your head from side to side, looking to the beach in hopes that someone, anyone, was there to help you.

 

There was no one.

 

The cock against your belly twitched as a second tentacle moved to your cunt, sliding itself deep into you. It grew thicker the further in it went, and you felt the beginnings of warmth begin to simmer in your belly. You whined in your throat and continued to shake your head, eyes shut tight to try and stem off whatever it was that was rising within you.

 

“No, no, no, please…”

 

He made a low creaking noise, deep in his throat, and you felt the tentacle in your cunt start to thrust itself in and out of your core. The one circling your clit grew faster, making tight circles, and the ones holding your legs drew them even further apart. There was no hope for you to escape.

 

The pleasure bubbling up in your lower belly pulled a moan from you, and you bit your lip hard enough to draw blood.

 

You had three options here, the way you saw it.

 

You could reject him, end up getting raped, and then be left to drown.

 

You could somehow fight him off, and be left to drown.

 

Or…

 

Your inner walls tightened around the tentacle deep inside you, and you shuddered at the growl that it pulled from him.

 

…was it really so bad, letting this happen? You’d be lying if you’d said you weren’t at least a little into it. You were just fighting it so hard because it seemed… wrong. He was a monster. An actual, legitimate monster. But you’ve had your hands free this whole time, and you haven’t struck at him once…

 

Maybe… maybe it’d be okay, if you just…

 

You slide your hand down his bony ‘stomach’ and wrap your fingers gingerly around his cock. The tentacles all freeze for a moment, and his head snaps down to look at you. You shiver beneath his gaze, but offer a small smile and, in hopes of communicating your willingness, slide your palm over the length of his dick. He shudders and growls again, and the movement of the tentacles at your cunt and clit seem to increase.

 

An orgasm is ripped from you, and your body seizes slightly in the inky black waters, inner walls clenching around his tentacle rhythmically. When you finally calm from your orgasm, you feel him sinking lower into the water, and you panic, for a brief moment. You begin to thrash, but he calms you with a quiet shushing sound, and he moves closer.

 

You feel the head of that large cock against your core, and you shudder, a rush of warmth going through you despite the coolness of the water around you. He stays like that, though, not moving until you meet his gaze and nod at him. He smirks at you, an incredibly sexy expression to be had on his face- er, skull… then he’s suddenly pressing inside. You moan and writhe as the stretch burns your inner walls, not enough to be unbearable, but enough to hurt. The bulbous base presses against you hard, and you can hear a gurgling hiss come from him.

 

His pace is unapologetic and rough, but you find yourself clinging to his shoulders as he fucks you, long and hard. The tentacles wrapped around your ankles pull on your legs until they are spread wide for him, and there is nothing stopping him from his brutal pace. A second orgasm crashes over you, and, oversensitive, you realize that he’s not yet done.

 

When he begins to growl with every exhale and his hips are bruising against yours, finally, finally he seems to be getting close. You rub your hands over his shoulders and his vertebrae, scratching lightly at where they all connect, and he finally comes undone. One tentacle shakily moves to circle your clit as he fucks you through his climax, hot seed spurting into your core, and he manages to pull a third and final orgasm from you just as he shoves the bulbous base of his cock inside, tying you to him.

 

You writhe together for a moment, lost in pleasure as he continues to pour an unfathomable amount of seed inside you. When he finally seems to calm himself, he releases his hold of your legs and instead uses his arms to pull you close to him. You wrap your legs around his waist and float with him, pressing kisses to his jawline and giggling when he lets out a trilling chirp-like sound.

 

Sitting in the afterglow, you take a moment to realize just what’s happened.

 

Gaster, the monsterous entity of the ocean, saved your life… then fucked you.

 

Tired, you yawn as your eyes slip closed, the dots of purple light lulling you into rest. This would make a pretty interesting story to tell your friends, at least.


End file.
